Oscillating disk rheometer

ABSTRACT

Method and apparatus for determining the rheological properties of an elastomer which method comprises subjecting a sample of the elastomer enclosed under pressure in a non-circular chamber, the base of which is star-shaped or rectangular, to oscillating shearing stress and measuring the stress. Dynamic properties are determined by enclosing a sample of the elastomer under pressure in a chamber, subjecting it to oscillating shearing stress at high frequency to provide measurable difference in phase between stress and displacement, measuring the torque required to impose the shearing stress and simultaneously measuring displacement.

United States Patent Decker {451 Aug. 8, 1972 1 OSCILLATING DISKRHEOMETER 2,948,147 8/l960 Roelig ..73/89 72 l t l or George E DeckerMcLean va Primary Examiner-Jerry W. Myracle [73] Asslgneez MonsantoCompany, St. Louis, Mo. AttomeyRichard O. Zerbe, Neal E. Willis and .l.E. 221 Filed: Aug. 26, 1970 [2l] Appl. N0.: 67,279 ABSTRACT Method andapparatus for determining the rheological Rem! Appumflon Dam propertiesof an elastomer which method comprises [63] Continuation of S r No282,527, May 6, subjecting a sample of the elastomer enclosed under 19 3abandned which is a continuatiomin. pressure in a non-circular chamber,the base of which pan f 231,428 Oct 13, 1962 abam is star-shaped orrectangular, to oscillating shearing doned' stress and measuring thestress. Dynamic properties are determined by enclosing a sample of theelastomer [52] us CL 73/101 73/15 6 under pressure in a chamber,subjecting it to oscillat- {511 Int. Cl Gan 3/52 s shearing Stress athigh frequency to provide 58 Field surable difference in phase betweenstress and dis- 1 0 placement, measuring the torque required to impose324/88; 64/14 the shearing stress and simultaneously measuringdisplacement. [56] References Cited 11 Claims, 9 Drawing figures UNITEDSTATES PATENTS 3,182,494 5/1965 Beatty et al.............73/l5.6 X

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GEORGE E. DECKER PATENTEmus BIS?! 3.681.980

SHEEI l 0F 7 STIFFNESS- INCH POUNDS TORQUE PHASE ANGLE DEGREES INVENTOR.GEORGE E. DECKER P'ATENTEI JA B 1912 3.681. 980 sum 5 ar 7 STIFFNESS-lNCH POUNDS TORQUE N O 0 b- (O In f Y 1- 0 :2 n K) 10 I T I I l I IOOrMOONEY VRSCOSYTY INVENTOR, GEORGE E. DECKER 1? pca w' \Qbi PATENTEDAUB a1912 SHEET 8 BF 7 STIFFNESS \NCH POUNDS TORQUE INVENTOR.

GEORGE E. DECKER RM 051mm PATENTEU M 3 I972 SHEET 7 OF 7 INVENTOR.GEORGE E. DECKER 500% MODULUS (PSU OSCILLATING DISK RHEOMETER Thisapplication is a continuation of application Ser. No. 282,527 filed May6, 1963 now abandoned, a continuation in part of application Ser. No.231,428 filed Oct. 18, 1962 now abandoned.

This invention relates to a measuring apparatus for determining theproperties of plastic materials and especially for measuring thecomplete curing characteristics and dynamic properties of elastomersduring vulcanization.

Methods for determining the state of cure of rubbers have been thesubject of extensive investigations. The classical methods are generallybased upon physical properties of separate rubber specimens vulcanizedto different states of cure. These techniques are disadvantageous inrequiring the testing of a large number of individually preparedsamples.

Instruments have been devised for continuously recording the change instiffness of a rubber specimen throughout vulcanization but they havethe disadvantage that the rubber is not maintained under pressure duringvulcanization. This results in blowing, flowing and oxidation of thespecimen during vulcanization so that no real significance can beattached to modulus values. Other instruments are known which determinethe compression modulus throughout vulcanization of the rubber specimenunder pressure but they fail to provide a measure of the dynamicproperties. The M- oney viscometer lMooney, M., Ind. Eng. Chem. (Anal.Ed.) 6, 147 (i934) widely used to determine scorch, is not applicable tothe direct examination of curing characteristics except at very earlystates of cure.

The present invention provides a single instrument which measures thecomplete curing characteristics and dynamic properties of a single testspecimen maintained under pressure continuously throughoutvulcanization. In essence, it comprises a forced oscillator embedded ina constant volume of plastic material under pressure. Insertion andremoval of the sample is provided for by relatively movable statorsections closing about the oscillator. The oscillator moves through asmall arc while the specimen is heated and maintained under pressurethereby subjecting the plastic material to the shearing action of theoscillator. Both stress and strain are measured by appropriatetransducers. Stress is determined by means for indicating the torquerequired to apply the shearing stress and strain is determined by meansprovided simultaneously to measure the oscillatory displacement motion.Provisions are made for changing both frequency and strain. Thisinstrument provides a convenient tool for determining the scorch time,curing rate, time to optimum cure and change in dynamic properties of arubber specimen.

FIG. 1 is essentially a cross-sectional view of the apparatus includingpictorial representations of some associated features.

FIG. 2 is a schematic representation of a system for treating thesignals from the apparatus to determine phase angle.

FIG. 3 is a graph which illustrates the agreement between rheometerstiffness data and stress-strain data obtained by conventional means.

FIG. 4 is a graph which shows in-phase elastic modulus, S; the viscouscomponent of modulus, S", (righthand ordinate); and phase angle(lefl-hand ordinate), all plotted against cure time in minutes.

FIG. 5 is a graph which illustrates the relationship between rheometerdata (complex dynamic modulus, S") and Mooney data.

FIG. 6 is a graph which illustrates the recording of a sinusoidal stresssignal made by a recorder. Rheometer stiffness is recorded against timein minutes.

FIG. 7 is a graph wherein 300 percent modulus in pounds per square inchobtained by conventional methods is plotted against inch pounds oftorque obtained with the rheometer employing a cylindrical cavity andsquare cavity, respectively.

FIG. 8 is a surface view of a square die.

FIG. 9 is a surface view of a star die.

A vertical cross sectional view through the center of the rheometer isshown in FIG. 1. A sinusoidly oscillating disk I oscillates through asmall angle as for example, 2. Provision is made for varying theamplitude from 1 to 6. The upper and lower dies 2 and 2' form the testchamber and are mounted on metal platens 3 and 3' which may be aluminum.The platens are maintained at a specified temperature within a toleranceof ilF. by means of a temperature controller not shown. The cavity maybe opened for insertion and for removal of the test specimen but is heldclosed during the test by air cylinder 4. An 8 inch air cylinder is aconvenient size where the pressure is 50-60 pounds per square inch. Thesize of the test specimens can vary, but may conveniently comprise twodisks approximately onefourth inch in thickness and 1% inches indiameter. If the modulus of the cured stock exceeds certain limitingvalues depending upon the composition of the test material, circularshape is unsatisfactory.

For example, to obtain meaningful numbers above about 1,500 psi in thecase of a typical natural rubber tread stock containing 50 parts byweight of carbon black it was necessary to employ a non-circular testspecimen designed to prevent free rotation of the sample. Rubber shrinksduring cure and slippage of the rubber specimen may occur in a circulartest chamber when the stress becomes sufficiently high. Whatever theexplanation, a test chamber with a square base or other shape designedto prevent slippage of the sample by variation from a perfect circleavoided the plateau of modulus values observed with circular chambers.It is desirable to have as large a ratio of cavity size to rotor size asis feasible, but of course there are practical limits to cavity size. Ascavity size increases the instrument becomes too bulky and requires toomuch test sample for practical consideration. As the rotor size isreduced a point is reached where the signals become too weak forsatisfactory measurement.

The oscillating motion of the disk may be imparted by an eccentric 5which may be driven by a variable speed motor 6. The torque required tooscillate the disk and thus to apply shearing stress to the rubberspecimen is measured by a stress transducer 7 comprising strain gaugesbonded to the lever 8 which connects the disk to the eccentric. BaldwinSR-4 strain gauges are convenient for building the stress transducers toconvert stress into an electrical signal. The oscillatory displacementmotion of the disk is measured simultaneously by a differentialtransformer 9. This converts the mechanical strain into an electricalsignal.

The metal platens 3 and 3' contain circular heating elements 10 and 10'.Exemplary dimensions are 9 inch diameter metal platens, inch depth ofthe cavities containing the heating elements and the dies and 4 inchdiameter of the die cavity. The lower metal platen rests on housingelement 1 1 held in fixed relation to cylinder adapter plate 12 bysupporting rods 13 and 13'. The housing in turn rests on the base plate14. The shaft 15 contains the collet and draw bar assembly 16 and 16'.The disk is securely fastened to the shaft by the collet and draw barassembly. The spindle of the disk 17 and the collet opening arepreferably square to aid in eliminating slipping and play in theoscillating cycle. Friction of the shaft during oscillation is reducedby ball bearings 18 and 18'.

The torque measuring device may be calibrated by dead weight loading,the slight distortion of the lever being picked up by the sensitivestrain gauges. The sinusoidal signals from the two transducers arepreferably amplified and fed to appropriate data presentation devices.For example, dynamic properties at the higher frequencies may bedetermined by recording simultaneously the stress and strain signals onan oscillograph and the stress-strain ellipse presented on anoscilloscope. The dynamic modulus may be determined in known manner fromthe stress (actually torque) recorded on the oscillograph. The strainimparted by the oscillating movement could be represented as a sinewave. The resulting stress also has the characteristics of the sine wavebut differs in phase. The difference in phase, which difference is knownas the loss angle, may be determined by varying the resistance in acalibrated resistance-capacitance phase shift network located betweenthe stress signal and the oscilloscope until the stress and strainsignals are inphase as indicated by coincidence of the stress and straintracings. Under this condition the ellipse becomes a straight line. Lossangles as low as a few degrees can be measured with a precision of i0.2". The real and imaginary parts of the complex dynamic modulus can becalculated from the loss angle and the dynamic loss values in knownmanner. Payne, AR, and Scott, J.R., Engineering Design With Rubber,"Interscience Publishers, lnc., New York 1960, Chapter 2. In essence thisinvolves solution of a right triangle in a vector diagram where themeasured torque is the resultant, the side opposite the phase angle isthe viscous component and the adjacent side the elastic component of themodulus.

From subjecting a fixed volume of elastomer to shearing stress impartedby an oscillator the phase angle may be determined as explained above bycontinuously measuring torque required to move the oscillator,simultaneously therewith continuously measuring displacement of theoscillator and measuring the shift in phase required to bring the torquesignal into phase with the strain signal. The preferred method ofdetermining the phase angle is illustrated in more detail in FIG. 2. Thestress signal 19 and the strain signal 20 from the amplifier 21 areconnected to an oscilloscope 22. However, the stress signal is connectedthrough a calibrated resistance-capacitance phase-shift network 23comprising variable resistor 24 and capacitor 25. At the oscilloscope,one set of terminals receives the stress signal input 26 and a secondset of terminals receives the strain signal input 27. After starting theoscillator the phase-shift network is adjusted until the ellipse 28which appears on the oscilloscope collapses into a straight line. Asingle line is maintained on the oscilloscope by continual adjustment ofthe phase-shift network throughout the run. The phase angle may be readdirectly from the calibration curve relating dial readings of thephase-shift network to phase angle. The calibration is of coursecalculated in known manner from the frequency, resistance andcapacitance.

The machine is loaded by removing the disk from the cavity, insertingthe spindle through the center of one test piece and replacing the disk.The second test piece is placed on the top of the disk and the diesclosed, forcing the rubber to surround the disk and completely fill thecavity. The oscillatory speed of the disk may be varied widely dependingupon the purpose of the study. In service different rubber articles maybe subjected to much different rates of dynamic stress. In generalfrequencies up to 3,600 cycles per minute comprise the range of usualinterest but this is not to be taken as limitative. As an example ofoperation to measure dynamic properties the disk was oscillated over 2are at a frequency of 852 cycles per minute (14.2 cycles per second) andto measure curing characteristics it was oscillated at 1 cycle perminute over the same arc. The amplified stress signal may be recorded ona conventional strip chart recorder, not shown. The actual experimentalrecord of the strip chart will relate stiffness in inch pounds of torqueto time in minutes. From such a record chart at the lower frequency theusual curing parameters of a rubber stock such as scorch time, inductiontime, curing rate, optimum cure and reversion characteristics may beeasily determined. At this low frequency the effect of the viscouscomponent of the rubber is The phase-shifi network is unnecessary.

Excellent agreement of rheometer stiffness data with stress-strain datais demonstrated by FIG. 3. In this figure a plot of continuous rheometerstiffness obtained at a frequency of 1 cycle per minute at 144C. and 300percent modulus values obtained at various cure times on a sulfenamideaccelerated natural rubber tread stock are compared. For purposes ofcomparison both the rheometer and stress-strain data in FIG. 3 are interms of percent of their respective maximum stiffness or moduli. Itwill be appreciated that the usual vulcanization parameter may becompletely determined from a single rheometer run whereas to determinethese parameters completely by the usual techniques it is commonpractice to use a combination of stressstrain and Mooney viscosity data.The advantage of a single instrument and test procedure for determiningall of the desired parameters is obvious.

Since many of the practical applications of elastomers involve dynamicflexing, knowledge of the dynamic properties throughout vulcanization isimportant. Optimum values of some of the important dynamic values of arubber specimen do not necessarily coincide with optimum cure measuredby static means. By operating the rheometer at the higher frequenciesand measuring both stress and strain and the phase angle between them,values for the in-phase elastic modulus and the loss modulus due to theout-phase viscous component may be calculated. FIG. 4 is a chart of theinphase elastic modulus S, the out-phase viscous component of themodulus S" and the phase angle versus cure time obtained on asulfenamide accelerated SBR tread stock vulcanized at 144C. 8 and S" arein units of inch pounds of torque and may be considered as rubberstiffness factors. Results from two independent runs are plotted on FIG.4 and demonstrate excellent reproducibility. From the known dimensionsand geometry of the oscillating disk and sample cavity it is possible tocalculate the dynamic shear modulus but such calculations form no partof the present invention. Although the data presented in FIG. 4 areplotted from individual measurements of the total dynamic modulus, S",and the phase angle taken at various intervals, the phase angle and 8*may be recorded continuously with some reduction in precision by meansof a phase meter and alternating current recorders to give a continuousrecord throughout vulcanization.

Good correlation between the Mooney viscosity curve and the rheometercurve results when the curve for the complex dynamic modulus 5" isdetermined at the higher frequencies. FIG. 5 illustrates therelationship between the curve for complex dynamic modulus S" obtainedat frequencies of 14.2 cycles/second and Mooney viscosity data.

As pointed out above, it is desirable to operate at low oscillatingfrequencies in order to minimize efi'ect of viscosity of the elastomerwhen it is desired to evaluate curing characteristics of rubber. Forsuch purpose the strain signal may be ignored and the strem signalrecorded as a continuous function with time. Recording the completesinusoidal stress signal against time provides a convenient visualrepresentation of the progress of curing as illustrated by FIG. 6. Thisis an actual tracing made by a recorder using a sulfenarnide acceleratednatural rubber tread stock and relates inch pounds of torque to time.From such a curve it is a simple matter to pick optimum cure by simplyobserving the time at which stiffness reaches a The importance of cavitygeometry is illustrated by FIG. 7 in which 300 percent modulus isplotted against rheometer units. Rubber stocks having a wide range ofmodulus values up to 3,000 pounds per square inch were compounded, eachpoint on the curves being obtained with the identical rubber stock, onesample being cured in the rheometer and another in a press. The modulusin pounds per square inch was determined by conventional means andplotted on the vertical or Y axis against rheometer units plotted on thehorizontal or X axis. The same rotor was used to obtain all therheometer data, the only variable being the cavity geometry. In one casea cylindrical cavity approximately 1% inches in diameter was used and inthe other case a cavity with square base approximately 2 inches on eachside was used as illustrated in FIG. 8. In both cases the height of eachsection of the cavity was approximately one-fourth inch so that thetotal cavity height was one-half inch. The rotor was a bi-conical rotorof the type illustrated in FIG. 1 approximately IV: inches in diameterat the common base of the two cones. In the rheometer the stocks werecured and the optimum cure selected from the maximum on the cure curve.The rheometer units corresponding to optimum cure then related to thecorresponding modulus values for optimum cure. The modulus values wereobtained by heating the stocks for different periods of time in the formof sheets, dieing out dumbbell test strips and pulling the test stripson a Scott tensile tester. Optimum cure was selected and the 300 percentmodulus corresponding to it plotted. The fact that the units are indifferent dimensions (pounds per square inch and inch pounds of torque)is of no significance because the object is only to test for linearity.It will be noted that the relationship was linear when the rheometerunits were obtained by use of the non-circular test cavity but departeddecidedly from linearity with the round cavity.

Although a test cavity with a square base is convenient and preferred,other shapes designed to prevent slippage are suitable, as for exampleelliptical, star shaped as illustrated in FIG. 9 or rectangular. Ingeneral, a test cavity in the form of any hexahedron or parallelepipedwill avoid the limitations of a circular cavity. A cavity in the form ofrectangular parallelepiped, also known as a cuboid, is easier toconstruct than some irregular shape and is for that reason preferred.

The are through which the oscillator moves is of course a function ofthe strain. The angle of oscillation should not exceed that at which thetest material begins to pull away from the oscillator or from thesurface of the cavity to a detrimental extent. More particularly, theangle of rotation should be below that which correspom to the ultimateelongation of the test material. The numerical limits will varydepending upon the particular test stock and the geometry of theoscillator and test chamber, but the limits can be readily determinedunder the particular circumstances of a given situation.

The invention has been illustrated by use of an oscillating conical diskbut an oscillating cylinder or other oscillating member may be used. Theconical shape is in nowise necessary for practice of the invention butit does have the advantage of simplifying calculations of dynamicmodulus for reasons recorded in the literature. By use ofa conical diskwith similar upper and lower regions the rate of shear becomes constant.Roughened surfaces are much preferred to minimize possibility ofslippage but evidence was obtained with natural and SBR rubber stocksusing a smooth disk oscillating in a rubber sample contained in a smoothsurfaced die that no slipping occurred. The surfaces may be roughened bycross-hatching. Cross-hatches of 1/32 inch squares 0.0l5 inch deep areconvenient. Alternatively, radial V grooves may be inserted into thedisk. Where calculations derived from the data are not required thegeometry of the oscillating member is unimportant.

The rheometer can be used to evaluate the rheological properties ofunvulcanized elastomers. The viscosities of some elastomers and carbonblack masterbatches are too great to be determined by instrumentscurrently available, as for example the Mooney viscometer. The presentinstrument overcomes this difficulty. Indeed, the rheological propertiesof any of the elastomers may be evaluated.

It is intended to cover all changes and modifications of the examples ofthe invention herein chosen for purposes of disclosure which do notconstitute departures from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A measuring apparatus comprising test material enclosing means whichinclude a non-circular chamber the base of which is star shaped orrectangular, an oscillatory disk within the chamber in fixed relativeposition with clearance therebetween to provide a volume of testmaterial which cannot rotate, means for maintaining the test materialunder pressure in the chamber, means for rotatively oscillating the disktherein and a stress transducer to measure torque required to oscillatethe disk.

2. In a measuring apparatus an oscillator, drive means connected to theoscillator, relatively movable stator sections closing about saidoscillator in fixed cuboid relation thereto defining a cuboid testmaterial enclosure, means for maintaining the test material undercontinuous confining pressure in the enclosure, force means connected tothe drive means to mechanically oscillate the oscillator and imposeoscillating shearing force on the test material and means to measure theforce required for oscillation.

3. A measuring apparatus comprising test material enclosing means whichinclude a cuboid chamber, an oscillatory disk within the chamber infixed relative position with clearance therebetween to provide enclosedvolume of test material, means for maintaining the test material underpressure in the chamber, means for rotatively oscillating the disktherein and a stress transducer to measure torque required to oscillatethe disk.

4. Apparatus for measuring loss angle of an elastomer which comprisesmeans for subjecting a volume of elastomer under pressure to shearingstress imparted by an oscillator embedded within the elastomer, meansfor measuring the torque required to move the oscillator, means forsimultaneously therewith measuring the displacement of the oscillator,means for converting torque and displacement into electrical signals anda calibrated resistancecapacitance phase shift network for measuring theshift in phase required to bring the torque signal into phase with thedisplacement signal by varying the resistance thereof until the torqueand displacement signals are in phase.

5. Apparatus for measuring the loss angle of an elastomer whichcomprises means for subjecting a fixed volume of elastomer to shearingstress imparted by an oscillator embedded within the elastomer, meansfor transducing the torque required to move the oscillator into anelectrical signal, means for simultaneously therewith transducing thedisplacement of the oscillator into an electrical signal, means foramplifying both the torque and displacement signals, aresistancecapacitance phase-shift network, means for displaying theamplified displacement signal and means for adjusting the phase-shiftnetwork to maintain a straight line on the display means.

6. Method of measuring the rheological properties of solid elastomericmaterial which comprises enclosing a sample of the material underpressure in a non-circular chamber the base of which is star shaped orrectangular while subjecting the enclosed material to rotary oscillatingshearing stress through an angle of rotation below that corresponding tothe ultimate elongation of the test material and measuring the torquerequired to move the oscillator.

8. Method of determining the curing characteristics of solid elastomericmaterial which comprises curing a sample of the material enclosed underpressure in a cuboid chamber about 2 inches on each side and about 0.5inch high while subjecting the enclosed material to rotary oscillatingshearing stress by an oscillating disk of about 1.5 inch diameterembedded within the material of low frequency such that effect of theviscous component of the elastomer is minimized and through an angle ofrotation below that corresponding to the ultimate elongation of thematerial and measuring the torque required to oscillate the disk.

9. Method of measuring the dynamic properties of solid elastomericmaterial which comprises curing a sample of the material enclosed underpressure in a euboid chamber while subjecting the enclosed material torotary oscillating shearing stress by an oscillating disk embeddedwithin the material oscillating at high frequency to provide measurabledifference in phase between stress and displacement and through an angleof rotation below that corresponding to the ultimate elongation of thematerial, measuring the torque required to oscillate the disk,simultaneously measuring displacement of the disk and determining phaseangle or a component of torque.

10. Method of measuring the dynamic properties of solid vulcanizableelastomeric material during vulcanization thereof which comprisesenclosing a sample of the material under pressure in a chamber,subjecting the enclosed material to vulcanim'ng conditions and duringthe vulcanization to rotary oscillating shearing stress at highfrequency to provide measurable differences in phase between stress anddisplacement and through an angle of rotation below that correspondingto the ultimate elongation of the material, measuring the torquerequired to impose the shearing stress, simultaneously measuringdisplacement and determining phase angle or a component of torque.

l l. The method of claim 10 wherein the frequency is about 852 cyclesper minute.

l I I 1 I!

1. A measuring apparatus comprising test material enclosing means whichinclude a non-circular chamber the base of which is star shaped orrectangular, an oscillatory disk within the chamber in fixed relativeposition with clearance therebetween to provide a volume of testmaterial which cannot rotate, means for maintaining the test materialunder pressure in the chamber, means for rotatively oscillating the disktherein and a stress transducer to measure torque required to oscillatethe disk.
 2. In a measuring apparatus an oscillator, drive meansconnected to the oscillator, relatively movable stator sections closingabout said oscillator in fixed cuboid relation thereto defining a cuboidtest material enclosure, means for maintaining the test material undercontinuous confining pressure in the enclosure, force means connected tothe drive means to mechanically oscillate the oscillator and imposeoscillating shearing force on the test material and means to measure theforce required for oscillation.
 3. A measuring apparatus comprising testmaterial enclosing means which include a cuboid chamber, an oscillatorydisk within the chamber in fixed relative position with clearancetherebetween to provide enclosed volume of test material, means formaintaining the test material under pressure in the chamber, means forrotatively oscillating the disk therein and a stress transducer tomeasure torque required to oscillate the disk.
 4. Apparatus formeasuring loss angle of an elastomer which comprises means forsubjecting a volume of elastomer under pressure to shearing stressimparted by an oscillator embedded within the elastomer, means formeasuring the torque required to move the oscillator, means forsimultaneously therewith measuring the displacement of the oscillator,means for converting torque and displacement into electrical signals anda calibrated resistance-capacitance phase shift network for measuringthe shift in phase required to bring the torque signal into phase withthe displacement signal by varying the resistance thereof until thetorque and displacemEnt signals are in phase.
 5. Apparatus for measuringthe loss angle of an elastomer which comprises means for subjecting afixed volume of elastomer to shearing stress imparted by an oscillatorembedded within the elastomer, means for transducing the torque requiredto move the oscillator into an electrical signal, means forsimultaneously therewith transducing the displacement of the oscillatorinto an electrical signal, means for amplifying both the torque anddisplacement signals, a resistance-capacitance phase-shift network,means for displaying the amplified displacement signal and means foradjusting the phase-shift network to maintain a straight line on thedisplay means.
 6. Method of measuring the rheological properties ofsolid elastomeric material which comprises enclosing a sample of thematerial under pressure in a non-circular chamber the base of which isstar shaped or rectangular while subjecting the enclosed material torotary oscillating shearing stress through an angle of rotation belowthat corresponding to the ultimate elongation of the test material andmeasuring the torque required to move the oscillator.
 7. The method ofclaim 6 wherein the chamber in which the elastomeric material isenclosed is cuboid and the shearing stress is applied by an oscillatorembedded within the material.
 8. Method of determining the curingcharacteristics of solid elastomeric material which comprises curing asample of the material enclosed under pressure in a cuboid chamber about2 inches on each side and about 0.5 inch high while subjecting theenclosed material to rotary oscillating shearing stress by anoscillating disk of about 1.5 inch diameter embedded within the materialof low frequency such that effect of the viscous component of theelastomer is minimized and through an angle of rotation below thatcorresponding to the ultimate elongation of the material and measuringthe torque required to oscillate the disk.
 9. Method of measuring thedynamic properties of solid elastomeric material which comprises curinga sample of the material enclosed under pressure in a cuboid chamberwhile subjecting the enclosed material to rotary oscillating shearingstress by an oscillating disk embedded within the material oscillatingat high frequency to provide measurable difference in phase betweenstress and displacement and through an angle of rotation below thatcorresponding to the ultimate elongation of the material, measuring thetorque required to oscillate the disk, simultaneously measuringdisplacement of the disk and determining phase angle or a component oftorque.
 10. Method of measuring the dynamic properties of solidvulcanizable elastomeric material during vulcanization thereof whichcomprises enclosing a sample of the material under pressure in achamber, subjecting the enclosed material to vulcanizing conditions andduring the vulcanization to rotary oscillating shearing stress at highfrequency to provide measurable differences in phase between stress anddisplacement and through an angle of rotation below that correspondingto the ultimate elongation of the material, measuring the torquerequired to impose the shearing stress, simultaneously measuringdisplacement and determining phase angle or a component of torque. 11.The method of claim 10 wherein the frequency is about 852 cycles perminute.